Flame retardancy phosphonic acid

MixedPhosphona.te Esters. Unsaturated, mixed phosphonate esters have been prepared from monoesters of 1,4-cyclohexanedimethanol and unsaturated dicarboxyhc acids. Eor example, maleic anhydride reacts with this diol to form the maleate, which is treated with benzenephosphonic acid to yield an unsaturated product. These esters have been used as flame-retardant additives for thermoplastic and thermosetting resias (97). 

This reaction is catalyzed by hydrogen chloride and yields can be essentially quantitative when using either free phosphonic acid or its diesters. The flame retardant, Eyrol 6, produced by Akzo Chemicals, Inc. and used for rigid urethane foams, is synthesized as follows (24). 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

The mechanism of the action of the phosphonate as a flame retardant is generally believed to be decomposition into acid fragments which contribute to char formation. These acidic species catalyze decomposition of the polyester, and give rise to species which on reaction with the phosphorus moiety cause char formation. TGA curves of the copolymers confirm that the incorporation of phosphorus into the polymer increases the char residue (Figure 4). These curves, however, show little evidence that the presence of phosphorus has any effect upon the temperature or rate of decomposition of the polyester. The curves are all fairly similar up to about 450°C. After that point, the amount of residue is proportional to the amount of phosphorus in the terpolymer. 

Quantitative risk assessments have been performed on a variety of flame-retardants used both in upholstered furniture fabric and foam. The National Research Council performed a quantitative risk assessment on 16 chemicals (or chemical classes) identified by the U.S. Consumer Product Safety Commission (CPSC). The results were published in 2000.88 The 16 flame-retardants included in this NRC study were HBCD, deca-BDE, alumina trihydrate, magnesium hydroxide, zinc borate, calcium and zinc molybdates, antimony trioxide, antimony pentoxide and sodium antimonate, ammonium polyphosphates, phosphonic acid, (3- [hydroxymethyl]amino -3-oxopropyl)-dimethylester, organic phosphonates, tris (monochloropropyl) phosphate, tris (l,3-dichloropropyl-2) phosphate, aromatic phosphate plasticisers, tetrakis (hydroxymethyl) hydronium salts, and chlorinated paraffins. The conclusions of the assessment was that the following flame-retardants can be used on residential furniture with minimal risk, even under worst-case assumptions ... 

The CPSC staff performed quantitative risk assessments on various flame-retardants for both upholstered residential furniture fabrics and foam.89 CPSC addresses chemical hazards under the Federal Hazardous Substances Act (FHSA), which is risk based. For fabrics, five flame-retardants were evaluated, that include antimony trioxide, deca-BDE, HBCD, phosphonic acid, (3- [hydroxymethyl]amino)-3-oxopropyl)-, dimethyl ester (PA), and tetrakis (hydroxymethyl) phosphonium chloride (THPC). These flame-retardants were selected for study because they are used to comply with the U.K. upholstered furniture flammability standard (except THPC) and fabric samples were available for testing. The staff concluded in 2006 that deca-BDE, HBCD, and PA would not present a hazard to consumers and that additional data would be needed to assess antimony trioxide and THPC. 

Also phosphorus- and nitrogen-containing polyols are shown to be effective in flame retardancy of PU foams24 such as polyols based on phosphonic acid ester or obtained by partial or full substitution of methylol groups of tetrakis(hydroxymethyl)phosphonium chloride with amine several examples of such polyols were reported by Levchik and Weil.15 Rigid PU foam modified with these polyols showed improved oxygen index values moreover better results were achieved with higher functionality polyols. 

Phosphine oxides, phosphonic acids, and phosphinic acids have been found to be flame retardants for various thermoplastic polymers. While there are many reasons for their effectiveness, we postulate that the acidity of the compounds is directly related to their activity and that the formation of polyphosphates (or phosphate glasses) is vital to the mechanism by which they function. 

In this paper we report the use of some phosphine oxides, phosphonic acids, and phosphinic acids to impart fire retardant properties to polymers. In addition, we postulate a mechanism by which these compounds behave as flame retardant agents. 

Table II. Phosphonic and Phosphinic Acids as Flame Retardants...

Mono- and diphosphonium halides have been found to be flame retardants for plastic materials. Their effectiveness can be related to the formation of various active phosphorus compounds, as well as to many of the postulated mechanisms for flame retardant action. The compounds are postulated to be effective because they decompose on ignition to thermally stable phosphine oxides or phosphonic acids which, in turn, are decomposed to continuous films of phosphate glass. In addition, the phosphonium halides form alkyl halides which cool the flame and/or form halogen acids which are fame retardants. 

Tn the preceding chapter (19) we described the use of phosphine A oxides, phosphonic acids, and phosphinic acids as flame retardants for thermoplastic materials. We also have found phosphonium halides to be effective flame retardants for plastics (5, 6). These compounds were either the monophosphonium halides,... 

Tetrakishydroxymethyl phosphonium chloride (THPC) is well established as a flame retardant agent with textiles (3). Collins (2) has suggested that THPC and urea break down to produce phosphoric acid via a phosphine oxide, phosphinic acid, and phosphonic acid. For cellulose, Collins concludes flameproofing is essentially caused by the dehydrating action of the phosphoric acid formed. 

As may be noted, major advances in the development of preparative rentes for tetracoordinated quinquevalent organophosphoms compounds occurred in the late nineteenth and early twentieth centuries. In more recent times, owing to increased applications and potential applications for derivatives of phosphonic and phosphinic acids, including biomedical regnlation, pest control, flame retardation, and biochemical mechanistic exploration, among others, increased attention has been given to approaches for the preparation of such materials. 

Applications In 1994 about half of the Phosphorus(III) chloride consumed in the USA was utilized in the manufacture of the intermediate phosphorous acid, a further 19.4% to phosphorus(V) oxychloride. Di and trialkylphosphonates, triarylphosphonate, pho.sphorus(V) sulfochloride and phosphorus(V) chloride are also manufactured directly from pho.sphorus(III) chloride. Broken down according to the field of application of the end products, the consumption of phosphorus(IIl) chloride is the USA in 1994 53.6% was utilized for pesticide production (mainly for glyphosphate), 18% for the manufacture of water treatment chemicals (phosphonic acids) and tensides (acid chlorides of fatty acids and secondary products), 17.1% in the manufacture of polymer additives (flame retardants, stabilizers etc.) as well as small quantities for the production of hydraulic fluids, lubricants and additives for lubricating oils. 

Neutral phosphonic acid esters are utilized as halogen-free flame retardants in plastics and textile fibers. 

Phosphonic acid derivatives have found wide read aj li-cations as flame retardants for plastics and textiles. 

The phosphonate polyols are characterised by the presence of -P-C- bonds which are very resistant to hydrolysis. The phosphonate polyols are one of the most important groups of reactive flame retardants - they are produced industrially and are used in many formulations, especially for rigid PU foams. The phosphonate polyols are esters of phosphonic acids (Figure 18.5) [1, 4-6, 11, 30, 34]. 

There are several possibilities for phosphonate polyol synthesis by Mannich reactions, Arbuzov reactions and by alkoxylation of phosphonic acids. Phosphonate polyols proved to be very efbcient flame retardants in practice. An important quality of these phosphorus polyols is the stability over time of formulated polyols containing phosphonate and water as reactive blowing agent, without a significant loss of their reactivity. 

Bellstein Handbook Reference) AI3-08678 BRN 0878263 CCRIS 876 DImethoxymethyl-phosphIne oxide Dimethyl methanephosphonate Di-methyl methylphosphonate DMMP EINECS 212-062-3 Fyrol DMMP HSDB 2590 Methyl phosphonic acid, dimethyl ester NCI-C54762 NSC 62240 Phosphonic add, methyl-, dimethyl ester Pyrol dmmp. Flame retardant for applications where high phosphorus content, good solvency, and low viscosity are desired lowers viscosity of epoxy resins and unsaturated polyesters filled with hydrated alumina oxide. Liquid bp = 181 , bp20 = 79.6" d ° = 1.4099 Am = 217 nm (e = 13, EtOH) soluble in H2O, Et20, EtOH LDsO (rat orl) > 5000 mg/kg. Akzo Chemie. 

Organophosphorus compounds (OPs) are utilized on a large scale as flame retarding agents and plasticizers in a variety of products, such as plastic materials, rubbers, varnishes, lubricants, hydraulic fluids, and other industrial applications. This family of chemicals consists of alkylated and arylated phosphate or phosphonate esters and related compounds such as phosphites, phosphines, and related dimeric forms as well as ionic forms (Figure 31.2). " The low volatility of phosphoric acid and derivatives makes it the preferred choice of the phosphorus based FRs. These FRs are most effective in polymers that char readily. Also halogenated phosphate esters, such as tris(l-chloroisopropyl) phosphate (TCPP), and tris(2-chloroethyl) phosphate (TCEP), are widely used. These combine the properties of both the halogen and the phosphorus compounds. 

Esters of orthophosphoric acid have been used extensively as plasticizers and lubricant additives. Others have been used as flame retardants. Many sulfur analogues find use as insecticides, while the introduction of P—C bonds give phosphonic and phosphinic acids. Esters of pyrophosphoric acid (H4P2O7) are also of interest as are amide derivatives. 

Synonyms Bis (P-chloroethyl) p-chloroethanephosphonate Di (2-chloroethyl)-2-chloroethanephosphonate Phosphonic acid, (2-chloroethyl)-bis(2-chloroethyl) ether Empirical C6H12CI3O3P Properties M.w. 269.49 Uses Flame retardant additive in rigid PU foams, rebonded foams, adhesives, coatings intermediate for bis(2-chloroethyl) vinylphosphonate, a flame-retardant monomer... 

Tetrakis (2-chloroethyl) ethylene diphosphate flame retardant, paper Aluminum hydroxide Ammonium bromide Ammonium phosphate, dibasic Ammonium polyphosphate Antimony trioxide Barium metaborate Bis (P-chloroethyl) vinyl phosphonate Boric acid Dimelamine phosphate Melamine phosphate Paraffin, chlorinated Perchloropentacyclodecane Zinc sulfide flame retardant, PBT... 

Ammonium bromide Ammonium phosphate, dibasic Ammonium polyphosphate Bis (3-chloroethyl) vinyl phosphonate Boric acid flame retardant, wool... 

Phosphorus-containing flame-retardants can also be incorporated into the polyester chain. Phosphonates enter the main chain while dialkyl phosphites form side chains through scission of the double bond of maleic acid. In addition allyl or diallyl phosphites may act as cross-linking agents. Ammonium polyphosphate is sometimes admixed to the resin as a filler. 

Ethenylidenebis(phosphonic acid) 1 and its esters have found utility as sequestering agents, in the development of polymeric flame retardants, and in certain pharmaceutical appheations. Ethenylidenebis(phosphonic acid) is prepared via the thermal dehydration of tetrasodium (l-hydroxyethylidene)bis(phosphonate) [165], Disadvantages of this time-consuming process include the need for precise control of temperature during the dehydration. 

The properties of polymers are hardly affected by the incorporation of phosphorus. Diesters of H-phosphonic acid and their inunediate derivatives have found a number of applications in polymer synthesis such as flame retardants, antioxidants, heat and Ught stabilizers, catalysts, degrading agents, and alkylating agents. They are also used as corrosion inhibitors, scale inhibitors, and lubricants (antiwear and load-carrying additives). 

The book contains chapters dealing with physical and spectral properties ( H, C, and NMR data) characteristic reactions important classes of compounds based on the esters of H-phosphonic add their application as physiologically active substances, flame retardants, catalysts, heat, and light stabilizers lubricants scale inhibitors polymer carriers of drugs preparation of diesters of H-phosphonic acid, and general procedures for conducting the most important reactions. 

Phosphorus-containing polymers, especially those comprising vinylphosphonic acid (VPA) and vinylphosphonate moieties, have become attractive polymers on an industrial scale, due to their various applications based on the properties of the phosphonic group. In early applications, poly(VPA) and its derivatives were noted as efficient scale inhibitors in cooling and boiler water systems, by inhibiting the formation of calcium sulfate, carbonate, and phosphate and as flame retardants." ... 

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